Hi Holly, I am a total Power Automate beginner. I have the same need as you had here. Would you be willing to share how you both copied one column/field (auto ID#) into another column initially for those existing SharePoint (list) records and to trigger it to happen for all new items added? I just for the life of me cannot figure out how to do it.
I have 2 fields/columns to copy into the same sharepoint list. (e.g. copy autogenerated ID and Created by into 2 separate columns,
i.e. ID number field copied into RefIDNo field
& Created By copied into RefRequestor field.